The present invention relates to field sensors and, in particular, to magnetic sensors for determining position and torque.
Magnetic sensing for determining a position or speed of a moving component is known and is used in applications such as power steering, braking, and motor control systems. Motor position sensing and steering wheel position sensing are similar in at least one way: access to the end of the moving shaft is generally limited or non-existent because the end of the shaft is connected to operating components. Thus, sensing is usually performed at the side of the shaft. For instance, a target magnet positioned on a shaft can be detected with a magnetic sensing element or sensor positioned concentric to the longitudinal axis of the shaft. In one application, the sensor may include components configured to count the number of times the shaft rotates. In a different application, the position of the shaft may be determined using several target magnets.
Resolvers and encoders are often used to process the raw information generated by the magnetic components. Resolvers provide an absolute output signal and encoders provide a relative output signal. The absolute nature of the signal from a resolver is desirable, but resolvers are often complex and expensive. Encoders are, in general, simpler and cheaper than resolvers, but can be inaccurate. In some cases, error detection hardware is used with encoders, but this adds complexity.